The wireless local area network (WLAN) technology known as “Wi-Fi” has been standardized by IEEE in the 802.11 series of specifications (i.e., as “IEEE Standard for Information technology—Telecommunications and information exchange between systems. Local and metropolitan area networks—Specific requirements. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”). The IEEE 802.11 specifications regulate the functions and operations of the Wi-Fi access points (APs) or wireless terminals, collectively known as “stations” or “STA,” in the IEEE 802.11 standards, including the physical layer protocols, Medium Access Control (MAC) layer protocols, and other aspects needed to secure compatibility and inter-operability between access points and portable terminals. Wi-Fi is commonly used as a wireless extension to fixed broadband access, e.g., in domestic environments and in so-called hotspots, like airports, train stations and restaurants. Most current Wi-Fi/WLAN deployments are totally separate from mobile radio networks, and can be seen as “non-integrated,” from the perspective of the user terminal.
Recently, Wi-Fi has been subject to increased interest from cellular network operators, who are studying the possibility of using Wi-Fi for purposes beyond its conventional role as an extension to fixed broadband access. These operators are responding to the ever-increasing market demands for wireless bandwidth, and are interested in using Wi-Fi technology as an extension of, or alternative to, cellular radio access network technologies (RATs). Cellular operators that are currently serving mobile users with, for example, any of the technologies standardized by the 3rd-Generation Partnership Project (3GPP), including the radio-access technologies known as Long-Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code-Division Multiple Access (WCDMA), and Global System for Mobile Communications (GSM), see Wi-Fi as a wireless technology that can provide good additional support for users of the operators' regular cellular networks.
In particular, 3GPP has studied ways to more tightly integrate LTE and WLAN, in particular for operator-deployed WLAN, so that traffic from WLAN-enabled user equipments (UEs—3GPP terminology for an access terminal) can be offloaded to WLAN from an eNodeB and vice versa. In early iterations of the standards for this integration, this tightened integration was achieved through semi-static policy setting, via Access Network Discovery and Selection Function (ANDSF) and/or offload thresholds broadcasted by the eNodeB (3GPP terminology for an evolved base station—also referred to as an “eNB”).
A 3GPP Rel-13 study item entitled Multi-RAT Joint Coordination has been recently started in 3GPP TSG RAN3 [3GPP TR 37.870]. The scope and requirements for the Multi-RAT Joint Coordination SI have been further defined in 3GPP working group meetings. In particular, for the 3GPP-WLAN coordination part, it has been agreed to focus on non-integrated 3GPP/WLAN nodes (i.e., as so-called standalone eNodeB and standalone AP), since integrated nodes are a matter of implementation.
Among the requirements of the study item [3GPP TR 37.870] is the investigation of potential enhancements of RAN interfaces and procedures to support the joint operation among different RATs, including WLAN. It has also been agreed that i) coordination involving WLAN and 3GPP is the priority of the study item, and ii) the statements on 3GPP/WLAN must be complementary to RAN2 work [R3-141512]. This complement could be achieved by the specification of an interface between the E-UTRAN and WLAN, which may occur in future releases of the standards.
The main functionality so far envisioned for this interface, called so far the “Xw interface,” is the support for traffic steering from LTE to WLAN via the reporting of different sets of information from WLAN to the eNodeB so that educated steering decisions can be taken. Also, 3GPP has recently approved a RAN2 work item on full network controlled 3GPP/WLAN traffic steering and aggregation [RP-150510, available at ftp://ftp.3gpp.org/tsg_ran/TSG_RAN/TSGR_67/Docs/RP-150510.zip], and thus new functionalities of the Xw interface can be envisioned.
As defined so far, the Xw interface is terminated in the eNodeB on the LTE network side, and in a logical node called WT (WLAN Termination) on the WLAN side. The WT can physically reside in an AP or in an AC and is assumed to have IP connectivity to the relevant WLAN nodes. Possible realization of the protocol and architectural of the Xw interface are depicted in FIGS. 1 and 2. Note that in the figures, the AP/AC has been assigned the role of the WT for the sake of clarity, but the WT node can be another node in the WLAN.
It is recognized herein that there are inefficiencies involved with Xw interface setup. Accordingly, improved techniques are needed for setting up the Xw interface or other interface between a radio access network node and a WT.